Toner dispenser logic control

ABSTRACT

A control device which regulates the dispensing of predetermined quantities of particles from a storage container to a mix for maintaining the concentration thereof substantially at a preselected level. The foregoing abstract is neither intended to define the invention disclosed in the specification, nor is it intended to be limiting as to the scope of the invention in any way.

[ Mall325, 1975 TONER DISPENSER LOGIC CONTROL m D U 2 2 a tm e u mfw HP0&6 Oi 0. km GGS 0 3 777 999 ill 932 l 8 5 353 627 277 333 [75]Inventors: James R. Davidson, Brighton; Carol A. Walter, Rochester, bothof NY.

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ABSTRACT A control device which regulates the dispensing ofpredetermined quantities of particles from a storage container to a mixfor maintaining the concentration thereof substantially at a preselectedlevel. The foregoing abstract is neither intended to define theinvention disclosed in the specification, nor is it [56] ReferencesCited UNITED STATES PATENTS intended to be limiting as to the scope ofthe invention Vw a W y n a .m 3 B w 2 2 WM ee LET. 5 No CD oo 66 99 H 4]Mm v w 8O 7O 23 12 Claims, 10 Drawing Figures PAIENIIED MIR? 5 5 3, 87300?.

SHEET 2 [IF 3 F l I I I I 1 I 62 I I Voltage I 2 l I 17?? ControlOscillator LOgiC Motor T P I I I l I Detector V Binary Counf Log:

Counter Detector Memory Dispense I r\ Timer 72 f 74 I gag DispenseIncrement Identification Binary Count Logic coumer Detector Memory A 7 725639 f'\ J\ f\ II I I Dispense Increment Low-Toner DefecoIdentification v {94 n02 {/M M n f 99 Binary Count Lag/c f er c untDetector Memory Dispense Timer 96 ;.98 Dispense Increment Low-Toner IDefecfor Identification I TONER DISPENSER LOGIC CONTROL BACKGROUND OFTHE INVENTION This invention relates generally to an electrophotographicprinting machine, and more particularly concerns a control device whichmeters predetermined quantities of toner particles from a toner particlestorage container to a developer mix utilized in the printing machinedevelopment system.

Various types of systems have been devised to regu late the addition oftoner particles to the developer mix. These systems are generallyarranged to monitor the concentration of toner particles in thedeveloper mix and furnish additional toner particles thereto asrequired. By maintaining toner particle concentration within thedeveloper mix at about a preferred value, the image density of the copyproduced by the printing machine remains substantially constant.

Heretofore, dispensing systems metered substantially constant quantitiesof toner particles into the developer mix of the development system. Thecontrol system sensed the concentration of toner particles within thedeveloper mix and produced an electrical signal indicative thereof. Onesuch system is disclosed in copending application Ser. No. 213,056 filedin 1971 now Pat. No. 3,754,821. As disclosed therein, an electricallybiased transparent electrode disposed on a photoconductive surfacepasses through the developer mix. While in the development Zone, thetransparent electrode attracts toner particles thereto. Subsequently,the electrode is illuminated and the density of toner particlesattracted thereto is indicated by the intensity of light passingtherethrough. A photosensor detects the intensity of light rays passingthrough the transparent electrode and develops an electrical signalproportional thereto. The electrical signal is compared with a referenceand a control signal is developed actuating the toner particle storagecontainer if the detected density is below the control point. Eachexcitation signal results in the actuation of the toner particle storagecontainer for a prescribed length of time during the next successivedevelopment cycle. In this manner, a relatively fixed guantity of tonerparticles are dispensed into the developer mix of the development systemwhen required. This type of system is known in the art as an ON-OFFsystem. By

this, it is meant that the concentration of toner particles in thedeveloper mix is sensed, and an electrical signal generated whichenergizes the toner particle storage container. Thus, if theconcentration of toner particles in the developer mix is beneath aspecified level, additional toner particles are supplied thereto.However, if the toner particle concentration is adequate, no electricalsignal is generated and the toner particle storage container remainsquiescent. In a system of this type, the amount of toner particlesdispensed into the developer mix during each development cycle must bemaintained within narrow limits. At the lower limits sufficient tonerparticles must be added to the developer mix to maintain satisfactoryimage density when toner particle demand is at a maximum. Contrawise,superfluous quantities of toner particles must not be added to thedeveloper mix during any one development cycle as this would produceexcessive image density. It is, therefore, apparent than an ON-OFFsystem of this type has a narrow latitude in order to attain theforegoing requirements.

Accordingly, it is a primary object of the present invention to improvethe control device for regulating the dispensing of toner particles froma toner particle storage container to the developer mix of a developmentsystem utilized in an electrophotographic printing machine.

SUMMARY OF THE INVENTION Briefly stated, and in accordance with thepresent invention, there is provided a control device for regulat' ingthe dispensing of predetermined quantities of particles from a storagecontainer to a mix.

Pursuant to the present invention, the control device includes detectingmeans and summing means. The detecting means senses the concentration ofparticles in the mix. In addition, the detecting means produces anelectrical signal indicating that the sensed particle concentration inthe mix is beneath a predetermined level. Summing means are provided todevelop a plurality of output signals corresponding to a discrete numberof detecting means electrical signals. Each summing means output signalactuates the storage container to dispense differing quantities ofpazrticlesinto the mix.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of thepresent invention will become apparent upon reading the followingdetailed description and upon reference to the draw ings in which:

FIG. I is a schematic perspective view of a multicolorelectrophotographic printing machine embodying the features of thepresent invention thereinz:

FIG. 2 is a block diagram of the control device of the present inventionemployed in association with the FIG. 1 printing machine;

FIG. 3 is a functional block diagram of the FIG. 2 control device;

FIG. 4 is a logic diagram of one of the blocks in the FIG. 3 functionalblock diagram;

FIG. 5 is a logic diagram of another of the blocks of the FIG. 3functional block diagram;

FIG. 6 is a logic diagram of another of the blocks of the FIG. 3functional block diagram;

FIG. 7 is a logic diagram of another of the blocks of the FIG. 3functional block diagram;

FIG. 8 is a logicdiagram of another of the blocks of the FIG. 3functional block diagram;

FIG. 9 is a logic diagram of another of the blocks of the FIG. 3functional block diagram; and

FIG. 10 is a logic diagram of another of the blocks of the FIG. 3functional block diagram.

While the present invention will be described in connection with apreferred embodiment thereof, it will be understood that it is notintended to limit the invention to that embodiment. On the contrary, itis intended to cover all alternatives, modifications and equivalents asmay be included within the spirit and scope of the invention as definedby the appended claims.

DETAILED DESCRIPTION OF THE INVENTION For a general understanding of thedisclosed multicolor electrophotographic printing machine in which thepresent invention may be incorporated, continued reference is had to thedrawings. In the drawings, like reference numerals have been usedthroughout to des ignate like elements. Turning now to FIG. 1, thevarious components of the multi-color printing machine are illustratedschematically therein. Although the control device of the presentinvention is particularly well adapted for use in this type ofelectrophotographic printing machine, it should become evident from thefollowing discussion that it is equally well suited for use in a widevariety ofelectrostatographic printing machines, and is not necessarilylimited in its application to the particular embodiment shown herein.

As depicted in FIG. 1, the electrophotographic printing machine utilizesa drum having a photoconductive surface 12 secured to the exteriorcircumferential surface thereof. Drum 10 is mounted rotatably on themachine frame and driven at a substantially constant angular velocity,in the direction of arrow 14, by a drive motor (not shown). As drum 10rotates, photoconductive surface 12 passes sequentiallythrough a seriesof processing stations. The drive motor rotates drum 10 at apredetermined speed relative to the other operating mechanisms of theprinting machine. The machine logic coordinates the timing of thevarious operations with the rotation of drum 10 to produce the propersequence of events at the respective processing stations.

Initially drum 10 rotates photoconductive surface 12 through chargingstation A. At charging station A, a co-' rona generating device,indicated generally at 16, extends longitudinally in a transversedirection across photoconductive surface 12. This readily enables coronagenerating device 16 to spray ions onto photoconductive surface 12 toproduce a relatively high, substantially uniform charge thereon.Preferably, corona generating device 16 is of a type described in US.Pat. No. 2,778,946 issued to Mayo in I957.

After photoconductive surface 12 is charged to a substantial uniformpotential, drum 10 is rotated to exposure station B. At exposure'stationB, a color filtered light image of original document 22 is projectedonto charged photoconductive surface 12. Exposure station B includes amoving lens system, generally designated by the reference numeral 18,and a color filter mechanism shown generally at 20. A suitable movinglens system is disclosed in U.S. Pat. No. 3,062,108 issued to Mayo in1962, and a suitable color filter mechanism is described in copendingapplication Ser. No. 830,282 filed in I969. Original document 22, suchas a sheet of paper, book, or the like is placed face down upontransparent viewing platen 24. As shown in FIG. 1, lamps 26 are adaptedto move in a timed relationship with lens 18 and filter mechanism 20toscan successive incremental areas of original document 22 disposedupon platen 24. In this manner, a flowing light image of the originaldocument 22 is projected onto photoconductive surface 12. During theexposure process, filter mechanism 20 interposes selected color filtersinto the optical light path of lens 18. The appropriate filter operateson the light rays transmitted through lens 18 to record an electrostaticlatent image on photoconductive surface 12 corresponding to apreselected spectral region of the electromagnetic wave spectrum,hereinafter referred to as a single color electrostatic latent image.

Drum 10 next rotates to a development station C. At development stationC, three individual developer units, generally indicated by thereference numerals 28, and 32, respectively are arranged to rendervisible the electrostatic latent image recorded on photoconductivesurface 12. Preferably, the developer units are all of a type generallyreferred to in the art as magresponding to the complement ofthe'spectral region of the wave length of light transmitted throughfilter 20. For example, a green filtered electrostatic latent image isdeveloped by depositing green absorbing magenta toner particles thereon,blue and red filtered latent images are developed with yellow and cyantoner particles, respectively. A typical development station employing aplurality of developer units, as disclosed in FIG. 1, is described incopending application Ser. No. 255,259, filed in 1972.

Pursuant to the present invention, additional toner particles are addedto the respective developer mixes when the concentration thereof isreduced beneath a specified level. The toner particle concentration isdetermined by detecting means, indicated generally at 34. Detectingmeans 34 includes a transparent electrode assembly 36 mounted onphotoconductive surface 12 of drum 10 in the non-image area thereof. Alight source 38, in cooperation with fiber optics 40 and 44, transmitsthe light rays through transparent electrode assembly 36 to photosensor42. As the electrostatic latent image recorded on photoconductivesurface 12 is developed, toner paricles are deposited on transparentelectrode 36. The intensity of the light rays passing throughtransparent electrode 36 is indicative of the density of toner particlesdeposited thereon. Photosensor 42 disposed in oven 46, receives thelight rays transmitted through transparent electrode 36. The logicelements, indicated generally at 60, of the present invention areadapted to process the electrical output signal from photosensor 42.Logic elements 60 will be described hereinafter in greater detail withreference to FIGS. 2 through 10, inclusive. The output from logicelements 60 actuate the respective toner particle storage container fordispensing toner particles into the developer mix of the appropriatedeveloper unit when the concentration thereof is beneath a prescribedlevel.

Proceeding now with the-various processes associated with themulti-color electrophotographic printing machine depicted in FIG. 1,after development, the now visible image is advanced to transfer stationD. At transfer station D, the toner powder image adheringelectrostatically to photoconductive surface 12 is transferred to asheet of final support material 50. Final support material 50 may beamongst others, plain paper or a sheet of thermoplastic polysulfonematerial. A transfer roll, shown generally at 52, secures supportmaterial 50 releasably thereto for movement in a recirculating paththerewith. Transfer roll 52 is adapted to rotate in synchronism withdrum 10 (in this case at substantially the same angular velocitytherewith). Hence, a plurality of toner powder images may be transferredfrom photoconductive surface 12 to support material 50, each tonerpowder image being superimposed in registration with the prior one.Image transfer is achieved by electrically biasing transfer roll 52 to apotential having sufficient magnitude and the proper polarity to attractelectrostatically toner particles from the latent image recorded onphotoconductive surface 12 to support material 50. US. Pat No. 3,612,677issued to Langdon et al. in 1971 describes a suitable electricallybiased transfer roll. Transfer roll 52 includes a recess thereinarranged to prevent photoconductive surface 12 from moving into contactwith the toner particles deposited on transparent electrode 36. Thus,the toner particles are not disturbed by the transfer process andrepresent a true indication of the toner particle concentration withinthe developer mix.

After a plurality of toner powder images have been transferred fromphotoconductive surface 12 to support material 50, support material 50is separated from the surface of transfer roll 52 and advanced to thefusing station (not shown). At the fusing station, the toner powderimage is permanently affixed to support material 50. One type ofsuitable fuser is described in US. Pat. No. 3,498,592 issued to Moseretal. in 1970 Support material 50, with the toner powder image affixedthereto, is, thereupon, advanced by conveyors (not shown) to a catchtray (not shown). The catch tray is arranged to permit the machineoperator to readily remove the completed copy from the printing machine.

The last processing station in the direction of rotation of drum 10, asindicated by arrow 14, is cleaning station E. As heretofore indicated, apreponderance of the toner particles are tranferred .to support material50, however, some residual toner particles remain on photoconductivesurface. 12. Cleaning station E removes these residual toner particlesfrom photoconductive surface 12. The residual toner particles areinitially brought under the influence of a cleaning corona generatingdevice (not shown) adapted to neutralize the remaining electrostaticcharge. Thereafter, the neutralized toner particles are cleaned fromphotoconductive surface 12 by arotating fibrous brush 56. Brush 56 ispositioned in contact with photoconductive surface 12. One type ofsuitable brush cleaning device is described in U.S. Pat. No. 3,590,412issued to Gerbasi in 1971.

lt is believed that the foregoing description is sufficient toillustrate the general operation ofa mul'ti-color electrophotographicprinting machine utilizing the teachings of the present inventiontherein.

FIG. 2 depicts a system to meter a predetermined quantity of tonerparticles into the developer mix of the corresponding developer units.As shown in FIG. 2, dashed lines represent a signal path within theprinting machine of FIG. 1, whereas solid lines refer to control logicsignals. Detecting means 34 develops an output voltage which is comparedto a reference voltage indicative of the desired toner concentrationwithin the corresponding developer mix. Comparator 58 determines thedifferences between the reference voltage developed by voltage source 57and the voltage generated by detecting means 34. This difference becomesan error signal which actuates control logic 60.

Control logic 60 will be described hereinafter with reference to FlGS. 3through 10, inclusive. One output from control logic 60 is an electricalsignal indicating that toner particles are depleted from the respectivetoner particle storage container. This signal in turn gencrates a signalactuating oscillator motor 62 of the toner particles storage containerto develop either a full or partial (in this case half) dispense oftoner particles therefrom. Another signal therefrom indicates the time 6in the print cycle that the'signal actuating the appropri ate tonerparticle storage container should be on or off. The toner particlesdispensed from the respective toner particle storage container increasethe concentration of toner particles in the developer mix and modify thedensity sensed by detecting means 34 on subsequent development cycles.Thus, the control system depicted in FIG. 2 is arranged to regulate theconcentration of toner particles within the developer mix of thecorresponding developer unit. However, the particular inventiondisclosed herein is directed to the detailed structural configuration ofcontro logic 60. This will be described hereinafter in greater detailwith reference to FIGS. 3 through 10, inclusive.

FIG. 3 illustrates a functional block diagram of control logic 60comprising three independent logic channels associated therewith.'Logicchannel 63 is associated with the cyan toner particles, logic channel 64is associated with the magenta toner particles, and logic channel 66'isassociated with the yellow toner particles. An electrical output signalfrom detecting means 34 is transmitted on line 68 to binary counter 70of the appropriate logic channel, in this case, the cyan logic channel.Binary counter 70 sums the number of electrical output signals fromdetecting means 34. lf the total number of electrical signals exceedsthe binary number 10, i.e., 1010, low-toner detection block 72 isactuated generating a signal which causes the printing machine to stopafter completion of the print-cycle. 1f the toner door (or in lieuthereof, the machine door) is opened and closed to add additional tonerparticles to the container, the low-toner condition is removed andbinary counter 70 reset to zero so that printing may resume.

In addition, an electrical output from binary counter 70 actuatesdispense increment indentification block 74. This, in turn, actuatesdispense time block 76, which determines the length of time that theoscillator motor is vibrated, thereby defining the length of the nexttoner dispense therefrom. Thus, if identification block 74 indicatedthat from one to three electrical output signals have been obtained fromdetecting means 34, i.e., 0001., 0010, or 0011, the left two binarynumbers being even (00), the toner dispense time will be a partialdispense, whereas if identification block 74 indicates that the numberof electrical outputsignals from detecting means 34 ranges from four toten, i.e., 0100, 0101, 0110, 0111,1000,1001, or 1010, the left binarynumber being odd (01 or 10), the toner dispense time will be a fulldispense time.

The output signal from binary counter also actuates count detector block78, which in turn energizes memory of a count block 80. Counter detector78 verities that there has been a request for toner particles, and logicmemory 80 provides a toner dispense signal. Logic memory 80 is energizedby a toner dispense signal from toner dispense time element 76 and fromcount detector 78. When the electrical signals from count detector 78and element 76 are both present memory element 80 is actuated. Element80 develops a toner dispense signal of the appropriate length whichenergizes the oscillator motor of the appropriate toner particle storagecontainer, in this case the cyan toner particle storage container.Developer length block is interconnected with cyan developer unit 32 anddetermines the length of time that cyan developer unit 32 is actuated.

Channels 64 and 66 are essentially the same as that of logic channel 63.Logic channel 64 actuates the magenta toner particle storage containerand includes binary counter 82 adapted to count the number of electricaloutput signals from detecting means 34. When binary counter 82 indicatesthat the total number of electrical output signals from the detectionmeans exceeds 10, low-toner detector 84 inhibits toner particledispensing. Toner dispensing increment identifier 86 indicates when thetotal number of electrical counts is intermediate four and ten. Thesignal therefrom ener giz'es toner dispense time block 88 which permitsa full dispense to be developed. Count detector 90 is actuated by binarycounter 82, and in association with a signal from dispense time 88actuates binary memory 92. If, however, from one to three electricaloutput signals have been summed from detecting means 34, element 88 willreduce the dispense time in half. Thus, the toner particle storagecontainer oscillator motor will be energized for about one-half the timeand about one-half the number of toner particles will be dispensed intothe magenta developer unit. Development length block 87 isinterconnected with magenta developer unit 30, and determines the lengthof time that magenta developer unit 30 is actuated.

In a similar fashion, logic channel 66 develops a full or partialdispense signal for the yellow toner particle storage container. Asdepicted in FIG. 3, binary counter 94 sums the number of electricaloutput signals from detecting means 34. If binary counter 94 indicatesthat ten electrical output signals have been produced by detecting means34, low-toner detection block 96 is actuated. Low-toner detection block96 thereupon inhibits yellow toner particle dispensing. The outputsignal from binary counter 94 also actuates the dispense incrementidentification block 98 which determines whether binary counter 94 isindicating an electrical output signal from detecting means 34 that isless than three or ranges from four to ten. Dispense incrementidentification block 98 actuates dispense timer 100. The output signalfrom binary counter 94 actuates count detector 102. The signal fromdispense timer 100 and count detector 102 actuates memory counter 104.Element 104, in turn, energizes the yellow toner particle storagecontainer oscillator motor for the time prescribed. Thus, if one tothree electrical output signals have been sensed, the yellow logicchannel oscillator motor is energized for a half dispense cycle.However, if four to ten electrical output signals have been sensed fromdetecting means 34, the oscillator motor of the yellow toner particlestorage container is actuated for a full dispense cycle. Developerlength block 99 is interconnected with yellow developer unit 28, anddetermines the length of time that yellow developer unit 28 is actuated.

The present invention has been described in connection with a pair ofoutput signals for energizing the oscillator motor such that the tonerparticle storage container discharges two differing quantities of tonerparticles into the developer mix. However, one skilled in the art willappreciate that a plurality of output signals may be used for energizingthe oscillator motor such that the toner particle storage containerdischarges a plurality of differing quantities of toner particles intothe developer mix.

Referring now to FIGS. 4 through 10, inclusive, the detailed logicelements utilized to form'the blocks of FIG. 3 will be discussed. Thelogic elements used to formulate the blocks of FIG. 3 are substantiallyidentical for each channel. Accordingly, the following description willdescribe the logic elements of the blocks for channel 62 of FIG. 3, theblocks for the remaining channels being the same. 7

Turning initially to FIG. 4, the logic elements of developer lengthlogic block will be described. The de-- veloper signal generated bylogic block 75 determines the length of time that developer unit 28 isin operation. As shown in FIG. 1, control 60 is interconnected withdeveloper unit 28, i.e., logic block 75 of control logic 60 isinterconnected therewith. Developer unit 28 remains operative for an 8%inch by l 1 inch long image one predetermined time interval, and for an11 inch by 14 inch long image a second predetermined time interval.Preferably, developer length logic block 75 includes NAND gate 106, NANDgate l08, and NAND gate 110. The output signals from the foregoing NANDgates energize NAND gate 112. The output from NAND gate 112 energizesdeveloper unit 28 for the requisite time duration.

With reference now to FIG. 5, toner dispense time block 76 is energizedby developer lengthblock 75. Toner dispense time block 76 is implementedso as to provide the other logic functions with the pulse duration ofthe developer signal. It provides a long dispense signal, e.g., when thebinary count ranges from 4 to 10, and a short dispense signal, e.g.,when the binary count ranges from 1 to 3. When the binary count is O thetoner particle storage containers are inhibited from dispensing tonerparticles therefrom. Block 76 includes NAND gate 114 which, inconjunction with an external signal energizes NAND gate 116. Inverter118 inverts the external signal and with two other external signalsactuates NAND gate 120. The output signals from NAND gate 116 and NANDgate 120 energize NAND gate 122. AND gate 124 is actuated by the outputsignal from NAND gate 122, the output of block 75, and an externalsignal. The output signal from AND gate 124 is utilized as an inputsignal to memory of a count block 80.

Turning now to FIG. 6, binary counter of dispense request block 70 isdepicted in detail therein. A count of O in binary, on the outputthereof indicates that no toner particles are dipensed from the tonerparticle storage container. A binary count ofl through 3, inclusive,indicates a half dispense, and a binary count of 4 through 10 inclusive,indicates a full dispense. A lowtoner shut down occurs in the printingmachine cycle following the tenth request to dispense toner particles.The count of the binary counter is enabled when the output fromcomparator 58 (FIG. 2) indicates that toner particles are not beingdeposited on transparent electrode 36 (FIG. 1), and a low-tonercondition does not exist. The binary counters are reset to zero countwhen the door for the housing of the toner particle storage container orin lieu thereof, the machine door, is opened and closed, or by aninitializing function obtained by turning the printing machine OFF andON. Preferably, logic block 70 includes AND gate 126 connected to binarycounter 128. The appropriate output signals from binary counter 128actuate low-toner detector block 72, dispense increment identificationblock 74 and detection of a count block 78.

Low-toner detection block 72 will now be described with reference toFIG. 7. Low-toner detection logic block 72 decodes the binarysignal fromthe output signal of binary counter 128. If a count of 10 is decoded, alow toner signal is generated. However, when the door to the housing ofthe toner particle storage'container is opened and closed, i.e.,additional toner particles are added to the toner particle storagecontainer, the low toner condition is removed since binary counter 128is reset to zero. Low-toner detection block 72 includes inverter 130 andinverter 132. The inputs to inverters 130 and 132 are output Signalsfrom counter 128. The output signals from inverters 130 and 132, inconjunction with the output signals from binary counter 128, energizedNAND gate 134. A negative output signal from NAND gate 134 inhibitsfurther dispensing of toner particles from the toner particle storagecontainer when a low-toner condition exists.

Turning now to FIG. 8, detection of a count block 78 will be describedin detail. Detection of acount block 78 includes inverter 136, inverter138, inverter 140 and inverter 142. The output signals from theforegoing inverters actuate NAND gate 144. The input signals toinverters 136, 138, 140and 142 are the outputs from binary counter 128.Inverters 136, 138, 140 and 142 in association with NAND gate 144operate in conjunction with one another as an OR function to verify thatthere has been a request for toner particles. The output signal fromNAND gate 144, and the output signal from AND gate 124 (FIG. energizememory of a count block 80.

FIG. 9 illustrates the logic element utilized to form dispense incrementblock 74. Preferably, dispense increment block 7.4 includes EXCLUSIVE OR146. EX- CLUSIVE OR 146 is actuated by the two left binary digits ofbinary counter 128. The output signal from EXCLUSIVE OR 146 is 0 whenthe two left binary digits are even, i.e., 00. However, the outputsignal from EXCLUSIVE OR 146 is 1 when the two left binary digits areodd, i.e., 01 or 10. A 0 output from EXCLU- SIVE OR 146 indicates a halfdispense signal, whereas a 1 output from EXCLUSIVE OR 146 indicates afull dispense signal. The output signal from EXCLUSIVE OR 146 actuatestoner dispense time block 76.

Finally, FIG. illustrates memory of a count block 80. Block 80,preferably, includes FLIP-FLOP 148 and AND gate 150. FLIP-FLOP 148 hasthe output thereof toggled i.e., set at 1, whenever both a tonerdispense time signal from block 76 and a count signal from block 78 arepresent. FLIP-FLOP 148 will remain at 1 until a 0 is toggled in by thetoner dispense time block 76 when there is no count signal from block78, or FLIP- FLOP 148 is reset by the printing machine logic. AND gate150 is used as the final pulse width determination of the toner dispensesignal.

In recapitulation, it is apparent that the control device'of the presentinvention meters a predetermined quantity of toner particles to thedeveloper mix so as to maintain the concentration thereof at asubstantially constant level. This is achieved by logic circuitry whichtotals the number electrical signals from the photosen sor to generateeither a full or partial dispense signal dependent upon number ofsignals received. In this manner, a predetermined quantity of tonerparticles are dispensed into the developer mix over a predetermined timeinterval. If the electrial output signal is such as to require a partialdispense, the time interval is reduced, whereas if the electrical outputsignal is such as to require a full dispense the time interval ismaintained at the full increment.

It is, therefore, apparent that there has been provided, in accordancewith this invention, a control device for metering predeterminedquantities of toner particles into the developer mix of a printingmachine development system that fully satisfies the objects, aims andadvantages set forth above. While this invention has been described inconjunction with specific embodiments thereof, it is evident that manyalternatives, modifications, and variations will be apparent to thoseskilled in the art. Accordingly, it is intended to embrace all suchalternatives, modifications and variations that fall within the spiritand broad scope of the appended claims.

What is claimed is:

1. A control device for regulating the dispensing of predeterminedquantities of particles from a storage container to a mix, including:

means for detecting the concentration of particles in the mix, saiddetecting means being arranged to provide an electrical signalindicating that the particle concentration within the mix is beneath apredetermined level; and

means for summing said detecting means electrical signals and providinga plurality of output signals each corresponding to a predeterminednumber of electrical signals, each output signal from said summing meansbeing adapted to actuate the storage container for dispensingpredetermined differing quantities of particles therefrom into the mix.said summing means provides a first output signal when the number ofelectrical signals from said detecting means is less than a firstpre-selected sum, the first output signal being adapted to actuate thestorage container for dispensing a first predetermined quantity ofparticles therefrom, and a second out put signal when the number ofelectrical signals from said detecting means is intermediate the firstpre-selected sum and a second pre-selected sum, the second output signalbeing adapted to actuate the storage container for dispensing a secondpredetermined quantity of particles therefrom.

2. A device as recited in claim ll, further including means foractuating the storage container, in response to the signal from saidsumming means, to dispense an amount of particles from the storagecontainer corre sponding to the output signal furnished thereto 3. Adevice as recited in claim 2, wherein said summing means includes:

means for counting the number of electrical signals from said detectingmeans;

means for generating the first output signal in response to saidcounting means indicating that the number of electrical signals fromsaid detecting means is less than the first pre-selected number ofelectrical signals; and

means, responsive to said counting means indicating that the number ofelectrical signals from said detecting means is intermediate the firstand second preselected number of electrical signals, for developing'thesecond output signal.

4. A device as recited in claim 3, further including means, responsiveto said counting means indicating that the number of electrical signalsfrom said detecting means is greater than the second preselected numberthereof, for producing a signal adapted to prevent said actuating meansfrom energizing the storage container for dispensing particlestherefrom.

5. A device as recited in'claim 4 further including means for resettingsaidcounting means to zero in response to said counting means indicatingthat the number of electrical signals from said detecting means isgreater than the second preselected number of electrical signals.

6. A device as recited in claim 5, wherein the second predeterminedquantity of particles dispensed from the storage container is greaterthan the first predetermined quantity of particles dispensed therefrom,the second predetermined quantity of dispensed particles beingpreferably about twice the amount of the first predetermined quantity ofdispensed particles.

7. An electrophotographic printing machine of the type having a tonerparticle storage container arranged to dispense predetermined quantitiesof toner particles therefrom into a developer mix utilized in adevelopment system thereof, including:

means for detecting the concentration of toner particles in thedeveloper mix, said detecting means being arranged to provide anelectrical signal indicating that the toner particleconcentration'within the developer mix is beneath a predetermined level;and

means for summing said detecting means electrical signals and providinga plurality of output signals each corresponding to a predeterminednumber of electrical signals, each output signal from said summing meansbeing adapted to actuate the toner particle storage container fordispensing predetermined differing quantities of toner particlestherefrom into the developer mix, said summing means provides a firstoutput signal when the number of electrical signals from said detectingmeans is less than a first pre-selected sum, the first output signalbeing adapted to actuate the toner particle storage container fordispensing a first predetermined quantity of toner particles therefrom,and a second output signal when the number of electrical signals fromsaid detecting means is intermediate the first pre-selected sum and asecond pre-selected sum, the second output signal being adapted toactuate the toner particle storage container for dispensing a secondpredetermined quantity of toner particles therefrom.

8. A printing machine as recited in claim 7, further including means foractuating the toner'particle storage container, in response to thesignal from said summing means to dispense an amount of toner particlesfrom the toner particle storage container corresponding to the outputsignal furnished thereto.

9. A printing machine as recited in claim 8, wherein said summing meansincludes:

means for counting the number of electrical signals from said detectingmeans;

means for generating the firstoutput signal in response to said countingmeans indicating that the number of electrical signals from saiddetecting means is less than the first preselected number of electricalsignals; and

means, responsive to said counting means indicating that the number ofelectrical signals from said detecting means is intermediate the firstand second preselected number of electrical signals, for developing thesecond output signal.

10. A printing machine as recited in claim 9, further including means,responsive to said counting means indicating that the number ofelectrical signals from said detecting means is greater than the secondpreselected number thereof, for producing a signal adapted to pre' ventsaid actuating means from energizing the toner particle storagecontainer for dispensing toner particles therefrom.

11. A printing machine as recited in claim 10, further including meansfor re-setting said counting means to zero in response to said countingmeans indicating that the number of electrical signals from saiddetecting means is greater than the second preselected number ofelectrical signals.

12. A printing machine as recited in claim 11, wherein the secondpredetermined quantity of toner particles dispensed from the tonerparticle storage container is greater than the first predeterminedquantity of toner particles dispensed therefrom, the secondpredetermined quantity of dispensed toner particles being preferablyabout twice the amount of the first predetermined quantity of dispensedtoner particles.

1. A control device for regulating the dispensing of predeterminedquantities of particles from a storage container to a mix, including:means for detecting the concentration of particles in the mix, saiddetecting means being arranged to provide an electrical signalindicating that the particle concentration within the mix is beneath apredetermined level; and means for summing said detecting meanselectrical signals and providing a plurality of output signals eachcorresponding to a predetermined number of electrical signals, eachoutput signal from said summing means being adapted to actuate thestorage container for dispensing predetermined differing quantities ofparticles therefrom into the mix, said summing means provides a firstoutput signal when the number of electrical signals from said detectingmeans is less than a first pre-selected sum, the first output signalbeing adapted to actuate the storage container for dispensing a firstpredetermined quantity of particles therefrom, and a second outputsignal when the number of electrical signals from said detecting meansis intermediate the first pre-selected sum and a second pre-selectedsum, the second output signal being adapted to actuate the storagecontainer for dispensing a second predetermined quantity of particlestherefrom.
 2. A device as recited in claim 1, further including meansfor actuating the storage container, in response to the signal from saidsumming means, to dispense an amount of particles from the storagecontainer corresponding to the output signal furnished thereto.
 3. Adevice as recited in claim 2, wherein said summing means includes: meansfor counting the number of electrical signals from said detecting means;means for generating the first output signal in response to saidcounting means indicating that the number of electrical signals fromsaid detecting means is less than the first pre-selected number ofelectrical signals; and means, responsive to said counting meansindicating that the number of electrical signals from said detectingmeans is intermediate the first and second preselected number ofelectrical signals, for developing the second output signal.
 4. A deviceas recited in claim 3, further including means, responsive to saidcounting means indicating that the number of electrical signals fromsaid detecting means is greater than the second preselected numberthereof, for producing a signal adapted to prevent said actuating meansfrom energizing the storage container for dispensing particlestherefrom. Pg,24
 5. A device as recited in claim 4 further includingmeans for resetting said counting means to zero in response to saidcounting means indicating that the number of electrical signals fromsaid detecting means is greater than the second preselected number ofelectrical signals.
 6. A device as recited in claim 5, wherein thesecond predetermined quantity of particles dispensed from the storagecontainer is greater than the first predetermined quantity of particlesdispensed therefrom, the second predetermined quantity of dispensedparticles being preferably about twice the amount of the firstpredetermined quantity of dispensed particles.
 7. An electrophotographicprinting machine of the type having a toner particle storage containerarranged to dispense predetermined quantities of toner particlestherefrom into a developer mix utilized in a development system thereof,including: means for detecting the concentration of toner particles inthe developer mix, said detecting means being arranged to provide anelectrical signal indicating that the toner particle concentrationwithin the developer mix is beneath a predetermined level; and means forsumming said detecting means electrical signals and providing aplurality of output signals each corresponding to a predetermined numberof electrical signals, each output signal from said summing means beingadapted to actuate the toner particle storage container for dispensingpredetermined differing quantities of toner particles therefrom into thedeveloper mix, said summing means provides a first output signal whenthe number of electrical signals from said detecting means is less thana first pre-selected sum, the first output signal being adapted toactuate the toner particle storage container for dispensing a firstpredetermined quantity of toner particles therefrom, and a second outputsignal when the number of electrical signals from said detecting meansis intermediate the first pre-selected sum and a second pre-selectedsum, the second output signal being adapted to actuate the tonerparticle storage container for dispensing a second predeterminedquantity of toner particles therefrom.
 8. A printing machine as recitedin claim 7, further including means for actuating the toner particlestorage container, in response to the signal from said summing means todispense an amount of toner particles from the toner particle storagecontainer corresponding to the output signal furnished thereto.
 9. Aprinting machine as recited in claim 8, wherein said summing meansincludes: means for counting the number of electrical signals from saiddetecting means; means for generating the first output signal inresponse to said counting means indicating that the number of electricalsignals from said detecting means is less than the first preselectednumber of electrical signals; and means, responsive to said countingmeans indicating that the number of electrical signals from saiddetecting means is intermediate the first and second preselected numberof electrical signals, for developing the second output signal.
 10. Aprinting machine as recited in claim 9, further including means,responsive to said counting means indicating that the number ofelectrical signals from said detecting means is greater than the secondpreselected number thereof, for producing a signal adapted to preventsaid actuating means from energizing the toner particle storagecontainer for dispensing toner particles therefrom.
 11. A printingmachine as recited in claim 10, further including means for re-settingsaid counting means to zero in response to said counting meansindicating that the number of electrical signals from said detectingmeans is greater than the second preselected number of electricalsignals.
 12. A printing machine as recited in claim 11, wherein thesecond predetermined quantity of toner particles dispensed from thetoner particle storage container is greater than the first predeterminedquantity of toner particles dispensed therefrom, the secondpredetermined quantity of dispensed toner particles being preferablyabout twice the amount of the first predetermined quantity of dispensedtoner particles.